Nervous systems possess adaptive features that facilitate the extraction of information from an environment. In particular, the cellular and subcellular constituents of neural circuits are capable of undergoing morphological, physiological and biochemical modifications in an experience-dependent manner. Long-term changes in the strength and number of synapses are thought to underlie how brains learn and adapt to the environment thereby modulating the behaviors of an organism. Olfaction, perhaps the most ethologically important sensory modality for rodents, provides cues which directly influence a variety of complex behaviors such as feeding, communication, predator recognition, and mating. Several studies have provided evidence that synaptic properties can be altered in response to sensory experience and during olfactory learning, although the exact mechanisms are unclear. Considering its proximity to the sensory periphery and the unique nature of input-output relationships, the mammalian olfactory system provides an attractive model for investigating activity-dependent plasticity. Using a combination of electrophysiological, optical imaging and molecular biological techniques, the aim is specifically to investigate activity-dependent refinement of juxtaglomerular neuron synapses in the mammalian olfactory bulb. A study of synaptic plasticity in the olfactory bulb may help discern basic principles by which a nervous system is regulated by an environment [unreadable] [unreadable]